ubifs: add full overlayfs support

Signed-off-by: Felix Fietkau <nbd@nbd.name>

4 files changed, 738 insertions, 0 deletions

diff --git a/target/linux/generic/patches-4.4/052-01-ubifs-Implement-O_TMPFILE.patch b/target/linux/generic/patches-4.4/052-01-ubifs-Implement-O_TMPFILE.patch
new file mode 100644
index 0000000000..957935c6af
--- /dev/null
+++ b/target/linux/generic/patches-4.4/052-01-ubifs-Implement-O_TMPFILE.patch
@@ -0,0 +1,99 @@
+From: Richard Weinberger <richard@nod.at>
+Date: Tue, 13 Sep 2016 16:18:55 +0200
+Subject: [PATCH] ubifs: Implement O_TMPFILE
+
+This patchs adds O_TMPFILE support to UBIFS.
+A temp file is a reference to an unlinked inode, a user
+holding the reference can use it. As soon it is being closed
+all data vanishes.
+
+Signed-off-by: Richard Weinberger <richard@nod.at>
+---
+
+--- a/fs/ubifs/dir.c
++++ b/fs/ubifs/dir.c
+@@ -301,6 +301,76 @@ out_budg:
+ 	return err;
+ }
+ 
++static int ubifs_tmpfile(struct inode *dir, struct dentry *dentry,
++			 umode_t mode)
++{
++	struct inode *inode;
++	struct ubifs_info *c = dir->i_sb->s_fs_info;
++	struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1};
++	struct ubifs_budget_req ino_req = { .dirtied_ino = 1 };
++	struct ubifs_inode *ui, *dir_ui = ubifs_inode(dir);
++	int err, instantiated = 0;
++
++	/*
++	 * Budget request settings: new dirty inode, new direntry,
++	 * budget for dirtied inode will be released via writeback.
++	 */
++
++	dbg_gen("dent '%pd', mode %#hx in dir ino %lu",
++		dentry, mode, dir->i_ino);
++
++	err = ubifs_budget_space(c, &req);
++	if (err)
++		return err;
++
++	err = ubifs_budget_space(c, &ino_req);
++	if (err) {
++		ubifs_release_budget(c, &req);
++		return err;
++	}
++
++	inode = ubifs_new_inode(c, dir, mode);
++	if (IS_ERR(inode)) {
++		err = PTR_ERR(inode);
++		goto out_budg;
++	}
++	ui = ubifs_inode(inode);
++
++	err = ubifs_init_security(dir, inode, &dentry->d_name);
++	if (err)
++		goto out_inode;
++
++	mutex_lock(&ui->ui_mutex);
++	insert_inode_hash(inode);
++	d_tmpfile(dentry, inode);
++	ubifs_assert(ui->dirty);
++	instantiated = 1;
++	mutex_unlock(&ui->ui_mutex);
++
++	mutex_lock(&dir_ui->ui_mutex);
++	err = ubifs_jnl_update(c, dir, &dentry->d_name, inode, 1, 0);
++	if (err)
++		goto out_cancel;
++	mutex_unlock(&dir_ui->ui_mutex);
++
++	ubifs_release_budget(c, &req);
++
++	return 0;
++
++out_cancel:
++	mutex_unlock(&dir_ui->ui_mutex);
++out_inode:
++	make_bad_inode(inode);
++	if (!instantiated)
++		iput(inode);
++out_budg:
++	ubifs_release_budget(c, &req);
++	if (!instantiated)
++		ubifs_release_budget(c, &ino_req);
++	ubifs_err(c, "cannot create temporary file, error %d", err);
++	return err;
++}
++
+ /**
+  * vfs_dent_type - get VFS directory entry type.
+  * @type: UBIFS directory entry type
+@@ -1189,6 +1259,7 @@ const struct inode_operations ubifs_dir_
+ #ifdef CONFIG_UBIFS_ATIME_SUPPORT
+ 	.update_time = ubifs_update_time,
+ #endif
++	.tmpfile     = ubifs_tmpfile,
+ };
+ 
+ const struct file_operations ubifs_dir_operations = {
diff --git a/target/linux/generic/patches-4.4/052-02-ubifs-Implement-RENAME_WHITEOUT.patch b/target/linux/generic/patches-4.4/052-02-ubifs-Implement-RENAME_WHITEOUT.patch
new file mode 100644
index 0000000000..9abb923932
--- /dev/null
+++ b/target/linux/generic/patches-4.4/052-02-ubifs-Implement-RENAME_WHITEOUT.patch
@@ -0,0 +1,342 @@
+From: Richard Weinberger <richard@nod.at>
+Date: Tue, 13 Sep 2016 16:18:56 +0200
+Subject: [PATCH] ubifs: Implement RENAME_WHITEOUT
+
+Adds RENAME_WHITEOUT support to UBIFS, we implement
+it in the same way as ext4 and xfs do.
+For an overview of other ways to implement it please
+refere to commit 7dcf5c3e4527 ("xfs: add RENAME_WHITEOUT support").
+
+Signed-off-by: Richard Weinberger <richard@nod.at>
+---
+
+--- a/fs/ubifs/dir.c
++++ b/fs/ubifs/dir.c
+@@ -301,8 +301,8 @@ out_budg:
+ 	return err;
+ }
+ 
+-static int ubifs_tmpfile(struct inode *dir, struct dentry *dentry,
+-			 umode_t mode)
++static int do_tmpfile(struct inode *dir, struct dentry *dentry,
++		      umode_t mode, struct inode **whiteout)
+ {
+ 	struct inode *inode;
+ 	struct ubifs_info *c = dir->i_sb->s_fs_info;
+@@ -336,14 +336,27 @@ static int ubifs_tmpfile(struct inode *d
+ 	}
+ 	ui = ubifs_inode(inode);
+ 
++	if (whiteout) {
++		init_special_inode(inode, inode->i_mode, WHITEOUT_DEV);
++		ubifs_assert(inode->i_op == &ubifs_file_inode_operations);
++	}
++
+ 	err = ubifs_init_security(dir, inode, &dentry->d_name);
+ 	if (err)
+ 		goto out_inode;
+ 
+ 	mutex_lock(&ui->ui_mutex);
+ 	insert_inode_hash(inode);
+-	d_tmpfile(dentry, inode);
++
++	if (whiteout) {
++		mark_inode_dirty(inode);
++		drop_nlink(inode);
++		*whiteout = inode;
++	} else {
++		d_tmpfile(dentry, inode);
++	}
+ 	ubifs_assert(ui->dirty);
++
+ 	instantiated = 1;
+ 	mutex_unlock(&ui->ui_mutex);
+ 
+@@ -371,6 +384,12 @@ out_budg:
+ 	return err;
+ }
+ 
++static int ubifs_tmpfile(struct inode *dir, struct dentry *dentry,
++			 umode_t mode)
++{
++	return do_tmpfile(dir, dentry, mode, NULL);
++}
++
+ /**
+  * vfs_dent_type - get VFS directory entry type.
+  * @type: UBIFS directory entry type
+@@ -997,37 +1016,43 @@ out_budg:
+ }
+ 
+ /**
+- * lock_3_inodes - a wrapper for locking three UBIFS inodes.
++ * lock_4_inodes - a wrapper for locking three UBIFS inodes.
+  * @inode1: first inode
+  * @inode2: second inode
+  * @inode3: third inode
++ * @inode4: fouth inode
+  *
+  * This function is used for 'ubifs_rename()' and @inode1 may be the same as
+- * @inode2 whereas @inode3 may be %NULL.
++ * @inode2 whereas @inode3 and @inode4 may be %NULL.
+  *
+  * We do not implement any tricks to guarantee strict lock ordering, because
+  * VFS has already done it for us on the @i_mutex. So this is just a simple
+  * wrapper function.
+  */
+-static void lock_3_inodes(struct inode *inode1, struct inode *inode2,
+-			  struct inode *inode3)
++static void lock_4_inodes(struct inode *inode1, struct inode *inode2,
++			  struct inode *inode3, struct inode *inode4)
+ {
+ 	mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_1);
+ 	if (inode2 != inode1)
+ 		mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_2);
+ 	if (inode3)
+ 		mutex_lock_nested(&ubifs_inode(inode3)->ui_mutex, WB_MUTEX_3);
++	if (inode4)
++		mutex_lock_nested(&ubifs_inode(inode4)->ui_mutex, WB_MUTEX_4);
+ }
+ 
+ /**
+- * unlock_3_inodes - a wrapper for unlocking three UBIFS inodes for rename.
++ * unlock_4_inodes - a wrapper for unlocking three UBIFS inodes for rename.
+  * @inode1: first inode
+  * @inode2: second inode
+  * @inode3: third inode
++ * @inode4: fouth inode
+  */
+-static void unlock_3_inodes(struct inode *inode1, struct inode *inode2,
+-			    struct inode *inode3)
++static void unlock_4_inodes(struct inode *inode1, struct inode *inode2,
++			    struct inode *inode3, struct inode *inode4)
+ {
++	if (inode4)
++		mutex_unlock(&ubifs_inode(inode4)->ui_mutex);
+ 	if (inode3)
+ 		mutex_unlock(&ubifs_inode(inode3)->ui_mutex);
+ 	if (inode1 != inode2)
+@@ -1036,12 +1061,15 @@ static void unlock_3_inodes(struct inode
+ }
+ 
+ static int ubifs_rename(struct inode *old_dir, struct dentry *old_dentry,
+-			struct inode *new_dir, struct dentry *new_dentry)
++			struct inode *new_dir, struct dentry *new_dentry,
++			unsigned int flags)
+ {
+ 	struct ubifs_info *c = old_dir->i_sb->s_fs_info;
+ 	struct inode *old_inode = d_inode(old_dentry);
+ 	struct inode *new_inode = d_inode(new_dentry);
++	struct inode *whiteout = NULL;
+ 	struct ubifs_inode *old_inode_ui = ubifs_inode(old_inode);
++	struct ubifs_inode *whiteout_ui = NULL;
+ 	int err, release, sync = 0, move = (new_dir != old_dir);
+ 	int is_dir = S_ISDIR(old_inode->i_mode);
+ 	int unlink = !!new_inode;
+@@ -1063,9 +1091,13 @@ static int ubifs_rename(struct inode *ol
+ 	 * separately.
+ 	 */
+ 
+-	dbg_gen("dent '%pd' ino %lu in dir ino %lu to dent '%pd' in dir ino %lu",
++	dbg_gen("dent '%pd' ino %lu in dir ino %lu to dent '%pd' in dir ino %lu flags 0x%x",
+ 		old_dentry, old_inode->i_ino, old_dir->i_ino,
+-		new_dentry, new_dir->i_ino);
++		new_dentry, new_dir->i_ino, flags);
++
++	if (flags & ~(RENAME_NOREPLACE | RENAME_WHITEOUT))
++		return -EINVAL;
++
+ 	ubifs_assert(mutex_is_locked(&old_dir->i_mutex));
+ 	ubifs_assert(mutex_is_locked(&new_dir->i_mutex));
+ 	if (unlink)
+@@ -1087,7 +1119,32 @@ static int ubifs_rename(struct inode *ol
+ 		return err;
+ 	}
+ 
+-	lock_3_inodes(old_dir, new_dir, new_inode);
++	if (flags & RENAME_WHITEOUT) {
++		union ubifs_dev_desc *dev = NULL;
++
++		dev = kmalloc(sizeof(union ubifs_dev_desc), GFP_NOFS);
++		if (!dev) {
++			ubifs_release_budget(c, &req);
++			ubifs_release_budget(c, &ino_req);
++			return -ENOMEM;
++		}
++
++		err = do_tmpfile(old_dir, old_dentry, S_IFCHR | WHITEOUT_MODE, &whiteout);
++		if (err) {
++			ubifs_release_budget(c, &req);
++			ubifs_release_budget(c, &ino_req);
++			kfree(dev);
++			return err;
++		}
++
++		whiteout->i_state |= I_LINKABLE;
++		whiteout_ui = ubifs_inode(whiteout);
++		whiteout_ui->data = dev;
++		whiteout_ui->data_len = ubifs_encode_dev(dev, MKDEV(0, 0));
++		ubifs_assert(!whiteout_ui->dirty);
++	}
++
++	lock_4_inodes(old_dir, new_dir, new_inode, whiteout);
+ 
+ 	/*
+ 	 * Like most other Unix systems, set the @i_ctime for inodes on a
+@@ -1157,12 +1214,34 @@ static int ubifs_rename(struct inode *ol
+ 		if (unlink && IS_SYNC(new_inode))
+ 			sync = 1;
+ 	}
+-	err = ubifs_jnl_rename(c, old_dir, old_dentry, new_dir, new_dentry,
++
++	if (whiteout) {
++		struct ubifs_budget_req wht_req = { .dirtied_ino = 1,
++				.dirtied_ino_d = \
++				ALIGN(ubifs_inode(whiteout)->data_len, 8) };
++
++		err = ubifs_budget_space(c, &wht_req);
++		if (err) {
++			ubifs_release_budget(c, &req);
++			ubifs_release_budget(c, &ino_req);
++			kfree(whiteout_ui->data);
++			whiteout_ui->data_len = 0;
++			iput(whiteout);
++			return err;
++		}
++
++		inc_nlink(whiteout);
++		mark_inode_dirty(whiteout);
++		whiteout->i_state &= ~I_LINKABLE;
++		iput(whiteout);
++	}
++
++	err = ubifs_jnl_rename(c, old_dir, old_dentry, new_dir, new_dentry, whiteout,
+ 			       sync);
+ 	if (err)
+ 		goto out_cancel;
+ 
+-	unlock_3_inodes(old_dir, new_dir, new_inode);
++	unlock_4_inodes(old_dir, new_dir, new_inode, whiteout);
+ 	ubifs_release_budget(c, &req);
+ 
+ 	mutex_lock(&old_inode_ui->ui_mutex);
+@@ -1195,7 +1274,11 @@ out_cancel:
+ 				inc_nlink(old_dir);
+ 		}
+ 	}
+-	unlock_3_inodes(old_dir, new_dir, new_inode);
++	if (whiteout) {
++		drop_nlink(whiteout);
++		iput(whiteout);
++	}
++	unlock_4_inodes(old_dir, new_dir, new_inode, whiteout);
+ 	ubifs_release_budget(c, &ino_req);
+ 	ubifs_release_budget(c, &req);
+ 	return err;
+@@ -1249,7 +1332,7 @@ const struct inode_operations ubifs_dir_
+ 	.mkdir       = ubifs_mkdir,
+ 	.rmdir       = ubifs_rmdir,
+ 	.mknod       = ubifs_mknod,
+-	.rename      = ubifs_rename,
++	.rename2     = ubifs_rename,
+ 	.setattr     = ubifs_setattr,
+ 	.getattr     = ubifs_getattr,
+ 	.setxattr    = ubifs_setxattr,
+--- a/fs/ubifs/journal.c
++++ b/fs/ubifs/journal.c
+@@ -917,14 +917,15 @@ int ubifs_jnl_delete_inode(struct ubifs_
+  * @sync: non-zero if the write-buffer has to be synchronized
+  *
+  * This function implements the re-name operation which may involve writing up
+- * to 3 inodes and 2 directory entries. It marks the written inodes as clean
++ * to 4 inodes and 2 directory entries. It marks the written inodes as clean
+  * and returns zero on success. In case of failure, a negative error code is
+  * returned.
+  */
+ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
+ 		     const struct dentry *old_dentry,
+ 		     const struct inode *new_dir,
+-		     const struct dentry *new_dentry, int sync)
++		     const struct dentry *new_dentry,
++		     const struct inode *whiteout, int sync)
+ {
+ 	void *p;
+ 	union ubifs_key key;
+@@ -980,13 +981,19 @@ int ubifs_jnl_rename(struct ubifs_info *
+ 	zero_dent_node_unused(dent);
+ 	ubifs_prep_grp_node(c, dent, dlen1, 0);
+ 
+-	/* Make deletion dent */
+ 	dent2 = (void *)dent + aligned_dlen1;
+ 	dent2->ch.node_type = UBIFS_DENT_NODE;
+ 	dent_key_init_flash(c, &dent2->key, old_dir->i_ino,
+ 			    &old_dentry->d_name);
+-	dent2->inum = 0;
+-	dent2->type = DT_UNKNOWN;
++
++	if (whiteout) {
++		dent2->inum = cpu_to_le64(whiteout->i_ino);
++		dent2->type = get_dent_type(whiteout->i_mode);
++	} else {
++		/* Make deletion dent */
++		dent2->inum = 0;
++		dent2->type = DT_UNKNOWN;
++	}
+ 	dent2->nlen = cpu_to_le16(old_dentry->d_name.len);
+ 	memcpy(dent2->name, old_dentry->d_name.name, old_dentry->d_name.len);
+ 	dent2->name[old_dentry->d_name.len] = '\0';
+@@ -1035,16 +1042,26 @@ int ubifs_jnl_rename(struct ubifs_info *
+ 	if (err)
+ 		goto out_ro;
+ 
+-	err = ubifs_add_dirt(c, lnum, dlen2);
+-	if (err)
+-		goto out_ro;
++	offs += aligned_dlen1;
++	if (whiteout) {
++		dent_key_init(c, &key, old_dir->i_ino, &old_dentry->d_name);
++		err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen2, &old_dentry->d_name);
++		if (err)
++			goto out_ro;
+ 
+-	dent_key_init(c, &key, old_dir->i_ino, &old_dentry->d_name);
+-	err = ubifs_tnc_remove_nm(c, &key, &old_dentry->d_name);
+-	if (err)
+-		goto out_ro;
++		ubifs_delete_orphan(c, whiteout->i_ino);
++	} else {
++		err = ubifs_add_dirt(c, lnum, dlen2);
++		if (err)
++			goto out_ro;
+ 
+-	offs += aligned_dlen1 + aligned_dlen2;
++		dent_key_init(c, &key, old_dir->i_ino, &old_dentry->d_name);
++		err = ubifs_tnc_remove_nm(c, &key, &old_dentry->d_name);
++		if (err)
++			goto out_ro;
++	}
++
++	offs += aligned_dlen2;
+ 	if (new_inode) {
+ 		ino_key_init(c, &key, new_inode->i_ino);
+ 		err = ubifs_tnc_add(c, &key, lnum, offs, ilen);
+--- a/fs/ubifs/ubifs.h
++++ b/fs/ubifs/ubifs.h
+@@ -180,6 +180,7 @@ enum {
+ 	WB_MUTEX_1 = 0,
+ 	WB_MUTEX_2 = 1,
+ 	WB_MUTEX_3 = 2,
++	WB_MUTEX_4 = 3,
+ };
+ 
+ /*
+@@ -1546,7 +1547,8 @@ int ubifs_jnl_delete_inode(struct ubifs_
+ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
+ 		     const struct dentry *old_dentry,
+ 		     const struct inode *new_dir,
+-		     const struct dentry *new_dentry, int sync);
++		     const struct dentry *new_dentry,
++		     const struct inode *whiteout, int sync);
+ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
+ 		       loff_t old_size, loff_t new_size);
+ int ubifs_jnl_delete_xattr(struct ubifs_info *c, const struct inode *host,
diff --git a/target/linux/generic/patches-4.4/052-03-ubifs-Implement-RENAME_EXCHANGE.patch b/target/linux/generic/patches-4.4/052-03-ubifs-Implement-RENAME_EXCHANGE.patch
new file mode 100644
index 0000000000..20856c347d
--- /dev/null
+++ b/target/linux/generic/patches-4.4/052-03-ubifs-Implement-RENAME_EXCHANGE.patch
@@ -0,0 +1,267 @@
+From: Richard Weinberger <richard@nod.at>
+Date: Tue, 13 Sep 2016 16:18:57 +0200
+Subject: [PATCH] ubifs: Implement RENAME_EXCHANGE
+
+Adds RENAME_EXCHANGE to UBIFS, the operation itself
+is completely disjunct from a regular rename() that's
+why we dispatch very early in ubifs_reaname().
+
+RENAME_EXCHANGE used by the renameat2() system call
+allows the caller to exchange two paths atomically.
+Both paths have to exist and have to be on the same
+filesystem.
+
+Signed-off-by: Richard Weinberger <richard@nod.at>
+---
+
+--- a/fs/ubifs/dir.c
++++ b/fs/ubifs/dir.c
+@@ -1095,11 +1095,6 @@ static int ubifs_rename(struct inode *ol
+ 		old_dentry, old_inode->i_ino, old_dir->i_ino,
+ 		new_dentry, new_dir->i_ino, flags);
+ 
+-	if (flags & ~(RENAME_NOREPLACE | RENAME_WHITEOUT))
+-		return -EINVAL;
+-
+-	ubifs_assert(mutex_is_locked(&old_dir->i_mutex));
+-	ubifs_assert(mutex_is_locked(&new_dir->i_mutex));
+ 	if (unlink)
+ 		ubifs_assert(mutex_is_locked(&new_inode->i_mutex));
+ 
+@@ -1284,6 +1279,64 @@ out_cancel:
+ 	return err;
+ }
+ 
++static int ubifs_xrename(struct inode *old_dir, struct dentry *old_dentry,
++			struct inode *new_dir, struct dentry *new_dentry)
++{
++	struct ubifs_info *c = old_dir->i_sb->s_fs_info;
++	struct ubifs_budget_req req = { .new_dent = 1, .mod_dent = 1,
++				.dirtied_ino = 2 };
++	int sync = IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir);
++	struct inode *fst_inode = d_inode(old_dentry);
++	struct inode *snd_inode = d_inode(new_dentry);
++	struct timespec time;
++	int err;
++
++	ubifs_assert(fst_inode && snd_inode);
++
++	lock_4_inodes(old_dir, new_dir, NULL, NULL);
++
++	time = ubifs_current_time(old_dir);
++	fst_inode->i_ctime = time;
++	snd_inode->i_ctime = time;
++	old_dir->i_mtime = old_dir->i_ctime = time;
++	new_dir->i_mtime = new_dir->i_ctime = time;
++
++	if (old_dir != new_dir) {
++		if (S_ISDIR(fst_inode->i_mode) && !S_ISDIR(snd_inode->i_mode)) {
++			inc_nlink(new_dir);
++			drop_nlink(old_dir);
++		}
++		else if (!S_ISDIR(fst_inode->i_mode) && S_ISDIR(snd_inode->i_mode)) {
++			drop_nlink(new_dir);
++			inc_nlink(old_dir);
++		}
++	}
++
++	err = ubifs_jnl_xrename(c, old_dir, old_dentry, new_dir, new_dentry,
++				sync);
++
++	unlock_4_inodes(old_dir, new_dir, NULL, NULL);
++	ubifs_release_budget(c, &req);
++
++	return err;
++}
++
++static int ubifs_rename2(struct inode *old_dir, struct dentry *old_dentry,
++			struct inode *new_dir, struct dentry *new_dentry,
++			unsigned int flags)
++{
++	if (flags & ~(RENAME_NOREPLACE | RENAME_WHITEOUT | RENAME_EXCHANGE))
++		return -EINVAL;
++
++	ubifs_assert(mutex_is_locked(&old_dir->i_mutex));
++	ubifs_assert(mutex_is_locked(&new_dir->i_mutex));
++
++	if (flags & RENAME_EXCHANGE)
++		return ubifs_xrename(old_dir, old_dentry, new_dir, new_dentry);
++
++	return ubifs_rename(old_dir, old_dentry, new_dir, new_dentry, flags);
++}
++
+ int ubifs_getattr(struct vfsmount *mnt, struct dentry *dentry,
+ 		  struct kstat *stat)
+ {
+@@ -1332,7 +1385,7 @@ const struct inode_operations ubifs_dir_
+ 	.mkdir       = ubifs_mkdir,
+ 	.rmdir       = ubifs_rmdir,
+ 	.mknod       = ubifs_mknod,
+-	.rename2     = ubifs_rename,
++	.rename2     = ubifs_rename2,
+ 	.setattr     = ubifs_setattr,
+ 	.getattr     = ubifs_getattr,
+ 	.setxattr    = ubifs_setxattr,
+--- a/fs/ubifs/journal.c
++++ b/fs/ubifs/journal.c
+@@ -908,6 +908,147 @@ int ubifs_jnl_delete_inode(struct ubifs_
+ }
+ 
+ /**
++ * ubifs_jnl_xrename - cross rename two directory entries.
++ * @c: UBIFS file-system description object
++ * @fst_dir: parent inode of 1st directory entry to exchange
++ * @fst_dentry: 1st directory entry to exchange
++ * @snd_dir: parent inode of 2nd directory entry to exchange
++ * @snd_dentry: 2nd directory entry to exchange
++ * @sync: non-zero if the write-buffer has to be synchronized
++ *
++ * This function implements the cross rename operation which may involve
++ * writing 2 inodes and 2 directory entries. It marks the written inodes as clean
++ * and returns zero on success. In case of failure, a negative error code is
++ * returned.
++ */
++int ubifs_jnl_xrename(struct ubifs_info *c, const struct inode *fst_dir,
++		      const struct dentry *fst_dentry,
++		      const struct inode *snd_dir,
++		      const struct dentry *snd_dentry, int sync)
++{
++	union ubifs_key key;
++	struct ubifs_dent_node *dent1, *dent2;
++	int err, dlen1, dlen2, lnum, offs, len, plen = UBIFS_INO_NODE_SZ;
++	int aligned_dlen1, aligned_dlen2;
++	int twoparents = (fst_dir != snd_dir);
++	const struct inode *fst_inode = d_inode(fst_dentry);
++	const struct inode *snd_inode = d_inode(snd_dentry);
++	void *p;
++
++	dbg_jnl("dent '%pd' in dir ino %lu between dent '%pd' in dir ino %lu",
++		fst_dentry, fst_dir->i_ino, snd_dentry, snd_dir->i_ino);
++
++	ubifs_assert(ubifs_inode(fst_dir)->data_len == 0);
++	ubifs_assert(ubifs_inode(snd_dir)->data_len == 0);
++	ubifs_assert(mutex_is_locked(&ubifs_inode(fst_dir)->ui_mutex));
++	ubifs_assert(mutex_is_locked(&ubifs_inode(snd_dir)->ui_mutex));
++
++	dlen1 = UBIFS_DENT_NODE_SZ + snd_dentry->d_name.len + 1;
++	dlen2 = UBIFS_DENT_NODE_SZ + fst_dentry->d_name.len + 1;
++	aligned_dlen1 = ALIGN(dlen1, 8);
++	aligned_dlen2 = ALIGN(dlen2, 8);
++
++	len = aligned_dlen1 + aligned_dlen2 + ALIGN(plen, 8);
++	if (twoparents)
++		len += plen;
++
++	dent1 = kmalloc(len, GFP_NOFS);
++	if (!dent1)
++		return -ENOMEM;
++
++	/* Make reservation before allocating sequence numbers */
++	err = make_reservation(c, BASEHD, len);
++	if (err)
++		goto out_free;
++
++	/* Make new dent for 1st entry */
++	dent1->ch.node_type = UBIFS_DENT_NODE;
++	dent_key_init_flash(c, &dent1->key, snd_dir->i_ino, &snd_dentry->d_name);
++	dent1->inum = cpu_to_le64(fst_inode->i_ino);
++	dent1->type = get_dent_type(fst_inode->i_mode);
++	dent1->nlen = cpu_to_le16(snd_dentry->d_name.len);
++	memcpy(dent1->name, snd_dentry->d_name.name, snd_dentry->d_name.len);
++	dent1->name[snd_dentry->d_name.len] = '\0';
++	zero_dent_node_unused(dent1);
++	ubifs_prep_grp_node(c, dent1, dlen1, 0);
++
++	/* Make new dent for 2nd entry */
++	dent2 = (void *)dent1 + aligned_dlen1;
++	dent2->ch.node_type = UBIFS_DENT_NODE;
++	dent_key_init_flash(c, &dent2->key, fst_dir->i_ino, &fst_dentry->d_name);
++	dent2->inum = cpu_to_le64(snd_inode->i_ino);
++	dent2->type = get_dent_type(snd_inode->i_mode);
++	dent2->nlen = cpu_to_le16(fst_dentry->d_name.len);
++	memcpy(dent2->name, fst_dentry->d_name.name, fst_dentry->d_name.len);
++	dent2->name[fst_dentry->d_name.len] = '\0';
++	zero_dent_node_unused(dent2);
++	ubifs_prep_grp_node(c, dent2, dlen2, 0);
++
++	p = (void *)dent2 + aligned_dlen2;
++	if (!twoparents)
++		pack_inode(c, p, fst_dir, 1);
++	else {
++		pack_inode(c, p, fst_dir, 0);
++		p += ALIGN(plen, 8);
++		pack_inode(c, p, snd_dir, 1);
++	}
++
++	err = write_head(c, BASEHD, dent1, len, &lnum, &offs, sync);
++	if (err)
++		goto out_release;
++	if (!sync) {
++		struct ubifs_wbuf *wbuf = &c->jheads[BASEHD].wbuf;
++
++		ubifs_wbuf_add_ino_nolock(wbuf, fst_dir->i_ino);
++		ubifs_wbuf_add_ino_nolock(wbuf, snd_dir->i_ino);
++	}
++	release_head(c, BASEHD);
++
++	dent_key_init(c, &key, snd_dir->i_ino, &snd_dentry->d_name);
++	err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen1, &snd_dentry->d_name);
++	if (err)
++		goto out_ro;
++
++	offs += aligned_dlen1;
++	dent_key_init(c, &key, fst_dir->i_ino, &fst_dentry->d_name);
++	err = ubifs_tnc_add_nm(c, &key, lnum, offs, dlen2, &fst_dentry->d_name);
++	if (err)
++		goto out_ro;
++
++	offs += aligned_dlen2;
++
++	ino_key_init(c, &key, fst_dir->i_ino);
++	err = ubifs_tnc_add(c, &key, lnum, offs, plen);
++	if (err)
++		goto out_ro;
++
++	if (twoparents) {
++		offs += ALIGN(plen, 8);
++		ino_key_init(c, &key, snd_dir->i_ino);
++		err = ubifs_tnc_add(c, &key, lnum, offs, plen);
++		if (err)
++			goto out_ro;
++	}
++
++	finish_reservation(c);
++
++	mark_inode_clean(c, ubifs_inode(fst_dir));
++	if (twoparents)
++		mark_inode_clean(c, ubifs_inode(snd_dir));
++	kfree(dent1);
++	return 0;
++
++out_release:
++	release_head(c, BASEHD);
++out_ro:
++	ubifs_ro_mode(c, err);
++	finish_reservation(c);
++out_free:
++	kfree(dent1);
++	return err;
++}
++
++/**
+  * ubifs_jnl_rename - rename a directory entry.
+  * @c: UBIFS file-system description object
+  * @old_dir: parent inode of directory entry to rename
+--- a/fs/ubifs/ubifs.h
++++ b/fs/ubifs/ubifs.h
+@@ -1544,6 +1544,10 @@ int ubifs_jnl_write_data(struct ubifs_in
+ 			 const union ubifs_key *key, const void *buf, int len);
+ int ubifs_jnl_write_inode(struct ubifs_info *c, const struct inode *inode);
+ int ubifs_jnl_delete_inode(struct ubifs_info *c, const struct inode *inode);
++int ubifs_jnl_xrename(struct ubifs_info *c, const struct inode *fst_dir,
++		      const struct dentry *fst_dentry,
++		      const struct inode *snd_dir,
++		      const struct dentry *snd_dentry, int sync);
+ int ubifs_jnl_rename(struct ubifs_info *c, const struct inode *old_dir,
+ 		     const struct dentry *old_dentry,
+ 		     const struct inode *new_dir,
diff --git a/target/linux/generic/patches-4.4/052-04-ubifs-Use-move-variable-in-ubifs_rename.patch b/target/linux/generic/patches-4.4/052-04-ubifs-Use-move-variable-in-ubifs_rename.patch
new file mode 100644
index 0000000000..81129359d3
--- /dev/null
+++ b/target/linux/generic/patches-4.4/052-04-ubifs-Use-move-variable-in-ubifs_rename.patch
@@ -0,0 +1,30 @@
+From: Richard Weinberger <richard@nod.at>
+Date: Tue, 13 Sep 2016 16:18:58 +0200
+Subject: [PATCH] ubifs: Use move variable in ubifs_rename()
+
+...to make the code more consistent since we use
+move already in other places.
+
+Signed-off-by: Richard Weinberger <richard@nod.at>
+---
+
+--- a/fs/ubifs/journal.c
++++ b/fs/ubifs/journal.c
+@@ -1100,7 +1100,7 @@ int ubifs_jnl_rename(struct ubifs_info *
+ 	aligned_dlen1 = ALIGN(dlen1, 8);
+ 	aligned_dlen2 = ALIGN(dlen2, 8);
+ 	len = aligned_dlen1 + aligned_dlen2 + ALIGN(ilen, 8) + ALIGN(plen, 8);
+-	if (old_dir != new_dir)
++	if (move)
+ 		len += plen;
+ 	dent = kmalloc(len, GFP_NOFS);
+ 	if (!dent)
+@@ -1216,7 +1216,7 @@ int ubifs_jnl_rename(struct ubifs_info *
+ 	if (err)
+ 		goto out_ro;
+ 
+-	if (old_dir != new_dir) {
++	if (move) {
+ 		offs += ALIGN(plen, 8);
+ 		ino_key_init(c, &key, new_dir->i_ino);
+ 		err = ubifs_tnc_add(c, &key, lnum, offs, plen);